How do I switch form Object mode to Edit mode, Weight Paint, Vertex Paint or Sculpt Mode mode in version 2.8?
To toggle between different modes use the keyboard number keys 

1 for Object Mode

2 for Edit Mode



3 for Weight Paint

4 for Vertex Paint

5 for Texture Paint

6 for Sculpt Mode



Source: https://youtu.be/t-EKbCJagqI?t=356